Male Anatomy: Understanding the Testes and Associated Functions

what is the primary function of the male reproductive system

manufacture and deliver sperm

what are the main components of the male reproductive system

1. spermatic cord

2. scrotum

3. testis

4. excurrent duct system

5. accessory sex glands

6. penis and muscles for protrusion, erection, and ejaculation

what is the function of the penis

copulatory organ

what are the 2 types of penises

fibroelastic and vascular

what species have a fibroelastic penis

boar, bull, ram, and buck

what species have a vascular penis

dogs, humans, and the stallion

what is the glans penis

the end of the penis

highly innervated, homologue to the clitoris

temperature and pressure sensitive to initiate ejaculation

what is the preputial fold in stallions

folds of skin on the penis

what is unique about the tom cat's penis

spines to aid in stimulation of the female for ovulation

cats are induced ovulators, have to be stimulated by these spines to ovulate

what species has a cartilaginous process on the penis

alpaca

define a fibroelastic penis

non-expandable with dense connective tissue

sigmoid flexure that allows the penis to expand and collapse under control of the retractor penis muscle

-when the retractor penis muscle is relaxed, the penis protrudes from the sheath

define a vascular penis

expandable with minimal connective tissue

what is unique about the dog's penis

has an os penis (baculum) made of bone

the bulbis glandis (BG) becomes enlarged during mating, forming a copulatory lock in the bitch's vagina

erection in the penis is controlled by

blood flow

what are the types of spongy erectile tissue in the interior of the penis

corpus cavernosum: spongy erectile tissue in penile interior

corpus spongiosum: ventral portion of penile urethra

rushing of blood into both of these tissues aids in erection for both fibro-elastic and vascular penises

erection and ejaculation are controlled by

muscles

what are the muscles of the penis

ischiocavernosus muscle, bulbospongiosus muscle, urethralis muscle

what is the ischiocavernosus muscle

paired muscle that connects the penis to the ischial arch

on the lateral sides of the penis, encloses and contracts around the crus penis to provide rigidity

-contracts the crus to hold blood inside the penis

what is the bulbospongiousus muscle

overlaps the penis root and contracts to empty the extra-pelvic urethra during ejaculation

what is the urethralis muscle

surrounds the pelvic urethra and moves sperm and seminal plasma into the urethra

describe the glans penis in the boar

corkscrew shape that fits into the interdigitating pads of the sow

describe the glans penis of the tom cat

spines to stimulate the vagina

-induces neural reflex to increase LH and induce ovulation

-the spines are androgen dependent and disappear after castration (need the presence of testosterone)

describe the glans penis of the alpaca

cartilaginous process

describe the glans penis of the ram

urethral process

which species have pendulous scrotum

bull, ram, and buck

describe the bull repro tract

pendulous scrotum

fibroelastic penis

sigmoid flexure

describe the stallion repro tract

vascular penis

ventral scrotum

describe the boar repro tract

ventral scrotum

-large testis due to their lack of seasonality and short gestation period (need a lot of sperm to breed sows year-round and produce a large volume of ejaculate)

fibroelastic penis

corkscrew glans penis

enlarged vesicular gland

-they produce a large gel fraction in the ejaculate that contributes most of the volume

describe the dog repro tract

ventral scrotum against the body

bulbus glandis

os penis

describe the tom repro tract

scrotum slightly ventral to anus

penis ventral to scrotum

penile spines

the testes need to be _______ ______ ________ than the rest of the body to maintain spermatogenesis

3-5 degrees C cooler

which species have internal testes

birds and marine mammals

describe repro in poultry and other birds

have a rudimentary penis

-cloacal kiss

-ducks are the only birds that have retained their penis which is lymphatic and inverts to expand. it is also androgen dependent and becomes larger with more testosterone (seasonality)

in the warehouse analogy, which part is high speed manufacturing

testis

in the warehouse analogy, which part is the finishing shops

the head and body of the epididymis

in the warehouse analogy, which part is warehouse and shipping

the tail of the epididymis

in the warehouse analogy, which part is final alterations and packaging

accessory sex glands

in the warehouse analogy, which part is the delivery system

penis

what is the spermatic cord

pathway from the body (inguinal ring) to the scrotum

what does the spermatic cord provide

vasculature

lymphatics

innervation

what are the functions of the spermatic cord

suspends the testis in the scrotum via the inguinal canal

pathway for vascular supply, lymph, nerves, and the ductus deferens

connects the testis to the abdominal body cavity

the spermatic cord contains which 2 anatomical structures

ductus deferens and the pampiniform plexus

what is the function of the ductus deferens

sperm transport from the testis to the urethra

what is the function of the pampiniform plexus

provides temperature regulation to the testis

counter current heat exchanger

-heat from arterial blood (39 degrees C) transferred to cooler venous blood (33 degrees C) leaving the surface to enter the body

-cools blood entering the testis (arterial blood) and warms blood returning to the body

-transfers testosterone as well

what muscle is contained in the spermatic cord

cremaster muscle

describe the cremaster muscle

striated muscle

-can contract but not for extended periods of time like smooth muscle can

support and pumping action on the pampiniform plexus to facilitate blood flow

raises the testis in fight or flight scenarios

what animals have no scrotum

birds, elephants, sloths, armadillos, whales, and dolphins

how and why do we castrate

cut the spermatic cord

for feed efficiency, behavior, meat quality, etc.

microanatomy of the spermatic cord includes

the visceral vaginal tunic (inside)

the parietal vaginal tunic (surrounds)

the pampiniform plexus is a network of

arteries and veins

testicular venous blood is cooled by

direct heat loss through the skin of the scrotum

what are the functions of the spermatic cord and PP

cool blood to testis

-maintains testis temp at 33 C < body temp which is 39 C

testosterone transfer

-high venous [T] transferred to low arterial [T] (the brackets = concentrated)

-elevated testosterone is required for spermatogenesis (~4 times higher than systemic)

what is the scrotum comprised of

2 lobed sac

what are the functions of the scrotum

protects and supports testis

temperature regulation

what are the 4 layers of the scrotum

1. scrotal skin

2. tunica dartos

3. scrotal fascia

4. parietal vaginal tunic

visceral vaginal tunic (testis)

describe the anatomy of the scrotum

thin layer of skin with low levels of fat and hair

many sweat glands to allow evaporative heat transfer (cooling)

innervated with sympathetic nerves (autonomic nervous system/fight or flight)

-activate thermo-receptors to increase panting and cooling

what is detrimental to the testes

chronic and elevated temperature

ex. excess fat in scrotum, prolonged sickness or increased ambient temperature

damages sperm DNA

reduces fertilization and subsequent embryo development

ram testis temperature is _____ ______ with respiratory rate

directly correlated

what is the tunica dartos

smooth muscle involved in temperature regulation

changes scrotal location relative to the body

-contracts when it's cold to bring the scrotum closer to the body

-relaxes when it's hot to move the scrotum further from the body

changes scrotal surface area

-decreases when the muscle contracts

-increases when the muscle relaxes

what is the function of the scrotal fascia

provides support

why is the tunica dartos able to elevate the testis for a longer period of time than the cremaster muscle

tunica dartos is smooth muscle which can contract for longer

cremaster muscle is striated and can only contract for a short period of time

what is the parietal vaginal tunic

lines the scrotum between the cavity and visceral vaginal tunic

prevents adhesions to allow for free floating testes

what is the primary reproductive organ of the male

the testes

what is the function of the testis

produce spermatozoa (sperm) and testosterone (hormones and proteins) and fluids (more so the accessory sex glands)

what are the 2 layers of the testicular capsule

visceral vaginal tunic: outer layer of testis proper

tunica albuginea: underneath the visceral vaginal tunic

what is the tunica albuginea

connective tissue layer under the visceral vaginal tunic

septal projection join with the mediastinum

contractions move sperm to the rete tubules to the mediastinum then to the efferent ducts

-sperm produced in the seminiferous tubules exit through the rete tubules, into the efferent ducts (vas efferens) and out the ductus deferens

is parenchyma is _____ and ______

interstitial and tubular

describe the interstitial quality of the parenchyma

cells, connective tissues, blood vessels, lymphatic, nerves, and leydig cells

what do leydig cells produce

testosterone

describe the tubular quality of the parenchyma

seminiferous tubules

where are sperm produced

seminiferous tubules

the seminiferous tubules are composed of

basal and adluminal compartment

the formation of spermatozoa begins

near the basement membrane of the seminiferous tubules

what are sertoli cells

nurse cells

only somatic cells in the seminiferous epithelium and help regulate spermatogenesis

what is the blood testes barrier

Barrier between cell development and blood provided by tight junctions and part of the nurse cell membrane.

no blood vessels or leydig cells in the adluminal compartment because anything in circulation would recognize sperm as foreign and kill it

sertoli cells are attached by _______ ________ and these form

tight junctions

form complexes that house early stages of sperm formation (spermatogonia and primary spermatocytes)

protect against immunological invasion gaining access to the adluminal compartments, therefore, protecting sperm from being recognized and destroyed

bind to immature sperm as they're essential to sperm development

the adluminal compartments and germinal epithelium contain

primary spermatocytes, seconday spermatocytes, and spermatids

the seminiferous epithelium is AKA and is composed of

germinal epithelium

basal and adluminal compartments

describe sertoli cells

somatic nurse cells for sperm

-bind FSH like granulosa cells in the ovary and binds testosterone

separates adluminal from basal compartment

tight junctional complexes attach adjacent sertoli cells

part of the blood testis-barrier: prevents immune cells and immunoglobulins from entering the adluminal compartment

germ cells develop along the

basement membrane

spermatocyte maturation can be identified based on location

what stage are spermatocytes at in the basal compartment

spermatogonium

-cells have completed mitosis but not meiosis so they're diploid (2N)

what stage are spermatocytes at in the adluminal compartment

primary and secondary spermatocytes and spermatids

-cells have completed meiosis and are now haploid (1N)

describe the blood-testis barrier

peritubular cells surround the seminiferous tubules and the sertoli cell junctional complexes to form the blood-testis barrier

peritubular cells protect against ____________ and peritubular myoid cells also prevent

immunoglobulins (antibodies) and immune cells (macrophages and lymphocytes)

large molecular weight material from entering the adluminal compartments

peritubular cells contract to (muscle)

facilitate transport of sperm into the rete tubules

what three ducts are in the excurrent duct system

efferent ducts

epididymal duct

ductus deferens

what is the function of the efferent ducts

to move sperm and fluid from the rete tubules to the epididymis

describe the rete tubules

where mature spermatids with tails have completed spermatogenesis

what do the ductus deferens contain

smooth muscle to transport sperm via muscle contractions from the tail of the epididymis to the ductus deferens

what are the functions of the epididymis

maturation of sperm

provides acquisition of motility to sperm

stores mature sperm

which part is considered extra gonadal

epididymis

testes = gonad

outside of the gonad (surrounds it)

what is the epididymis comprised of

head, body, and tail

where is the primary storage location of sperm

tail of the epididymis

contains sperm ready for ejaculation

what is the term for the head of the epididymis

caput

what is the term for the body of the epididymis

corpus

what is the term for the tail of the epididymis

cauda

sperm characteristics within the tail (cauda) of the epididymis

site of sperm storage (only distal tail sperm ejaculated)

-number of females serviced or ejaculations is dependent on distal sperm reserves

sperm have normal fertility, motility, and can bind to oocytes

the distal droplet has now migrated to the tail, indicating a mature sperm capable of fertilization

the epididymis is a _______, _____________ (________)

single, highly convoluted duct, 30-60m long

sperm characteristics within the head (caput) of the epididymis

sperm have no motility or fertility and a proximal cytoplasmic droplet

the head also possesses less sperm than the body and tail

sperm shed their _________ as they move through the body and tail of the epididymis and it ___________ ________ ______ _______

cytoplasm

migrates down the tail